A. Field of the Invention
This invention relates to the field of sealing open head drums and in particular to a lid for open head drums adapted to prevent leakage.
B. Background Art
Open head drums are commonly used in the shipment of all types of commodities. They are used the packaging of dry powders, paste, semi-solids, paints, viscous liquids and special applications. The success of open head drums has in part been due to the convenience of closing rings. After a gasket and a lid have been placed on the drum, a closing ring is conventionally placed over the lip of the lid and tightened by a bolt which draws projections on the ends of the closing ring closer together. This permits a very tight seal of the lid.
However, as the bolt is turned to draw the projections closer to each other, circular stress is placed on the rim of the lid. The major region of the lip rim is underneath the closing gasket and therefore cannot be compressed. However, the region of the lip between the projections of the closing ring may be forced to compress. This may cause a distortion or dimpling of the lid. It is at this dimple that most leakage may occur. This is very undesirable, especially when the drums are used for long-term storage of toxic waste.
Open head drums sealed with closing rings are tested for leak resistance by dropping them, filled to a predetermined substance weight, from a predetermined distance. The drums are dropped directly on the region of the projections of the closing rings. This causes the compressed region of the lip to get worse and may permit leakage.